1. Field of the Invention
The present invention relates to a connecting device for an illuminant handpiece mainly used for dental treatment
2. Prior Art
The cutting tool installed in the head of a dental handpiece is driven pneumatically or electrically. The drive force thus obtained is used to cut defective portions of teeth for treatment. Passages for a medium used to rotate the cutting tool are built in the grip section of the handpiece. In parallel with these passages, the passages for activation media such as water and air used to cool the rotation section of the handpiece or to remove tooth chips are also provided in some handpieces. These drive and activation media are supplied from the connection block provided at the rear end of the grip section. The supply pipes and/or flexible hose accommodating a bundle of conductors used to supply the above-mentioned media are connected to the connection block The connection between the grip section and the connection block is rotatable so that the flexible hose is not twisted during use and so that the grip can be used smoothly with little resistance. Furthermore, the connection is made separable. To ensure proper connection at this connection section, the means for connecting the passages of the above-mentioned drive and activation media has been invented in various types. In addition, an illumination means to light treatment portions has been provided recently for the handpiece equipped with the above-mentioned rotatable grip section to ensure higher convenience during dental treatment. As the above-mentioned illumination means, the following three methods have been practically used. (1) A method of transmitting light from a light source outside the handpiece to the head of the handpiece via a photoconductive substance (2) A method of transmitting light to the head by coaxially providing an illumination lamp on the connection surface of the connection block, by building in a photoconductive substance in the grip section and by facing the rear end of the photoconductive substance to the lamp. (3) A method of irradiating light from the head section via a photoconductive substance provided in the grip section by providing the illumination lamp in the grip section and by rotatably connecting the terminals of the lamp at a connection section of a connection block. (Problems to be solved by the invention) The above-mentioned illumination methods have the following defects. In the case of method (1), the flexibility of the connection tube is deteriorated since the photoconductive substance is built in the connection tube. In the case of method (2), the illumination lamp must be disposed at the center of the handpiece. Therefore, it is very difficult to properly allocate the space for lamp replacement and the space for the passages for the activation media, resulting in a larger pipe diameter at the connection section. In the case of method (3), the loss is small and the lamp can be easily replaced since the lamp can be disposed close to the external circumference of the handpiece. In addition, it is relatively easy to allocate space for lamp replacement and space for the passages. However, at the connection section between the grip section and the connection block, what is called a slip joint, wherein one of two terminals provided in the thrust direction is slidably contacted by the other terminal in the radial direction, is used to electrically connect the power supply terminals and the lamp terminals Due to this structure of the slip joint, it is inevitable that the connection section becomes larger in diameter. Accordingly, none of the above-mentioned methods is satisfactory in terms of structure or handling.